1. Field of the Invention
The present invention relates generally to optical switches, and particularly to optical switches employing movable MEMS mirrors.
2. Technical Background
Currently, the demand for bandwidth is increasing exponentially. Network designers are seeking ways to move network functionality from the electrical domain into the optical domain to thereby exploit the available bandwidth in single mode optical fibers. Many networks that are operational today employ relatively low-speed optical-electric conversion units at network nodes. These units convert light signals into electrical signals before switching, and reconvert them into light signals afterwards. The bandwidth of electronic switching equipment is limited to about 10 GHz. This represents an unacceptable bottleneck. A need exists for cross-connects and switches that operate in the optical domain to thereby avoid the conversion bottleneck immediately described above.
In one approach that has been considered, an optical switching fabric was fabricated using a planar waveguide array. Trenches were formed at the intersections of the input waveguides and the output waveguides to form switching cross-points. Micromirrors were positioned in the trenches to function as switching pixels. Electrodes were disposed within each cross-point, functioning as actuators. When an electrode was addressed, the micromirror moved within the trench.
This approach has a disadvantage in that the micromirror had an unreasonably slow switching response time. Two primary reasons for this slow response time were discovered. First, Van der Waals forces were produced by index-matching fluids in the trench. Second, the interaction of mechanical surfaces at both the microscopic and macroscopic level caused the micromirror and support plate to adhere to the substrate for a short period of time after switch actuation.
Thus, a need exists for an optical switch having the advantages of the MEMS optical switch, with improved response time. In particular, a need exists for a MEMS switch having an assisted-release mechanism for improving response time.
A MEMS switch having an assisted-release mechanism that improves response time is disclosed. The assisted-release mechanism is coupled to a pixel member having a plate disposed over a trench in a switch cross-point, and a mirror extending from the plate into the trench. The assisted-release mechanism applies a force to the pixel member to overcome Van der Waal and stiction forces to thereby improve the switch response time.
One aspect of the present invention is an optical device for directing a light signal. The optical device includes a pixel member adapted to move between a first quiescent switch state and a second active switch state. An assisted-release mechanism is coupled to the pixel member, the assisted-release mechanism applying a force to the pixel member in the second active state.
In another aspect, the present invention includes an optical switch for directing at least one light signal. The optical switch includes an optical substrate having at least one trench formed at the intersection of at least one first waveguide and at least one second waveguide. An electrical substrate is coupled to the optical substrate, the electrical substrate having at least one actuator disposed opposite to the at least one trench. The optical switch also includes at least one pixel coupled to the optical substrate and interposed between the trench and the actuator, the at least one pixel moving between a first quiescent switch state and a second active switch state. An assisted-release mechanism is coupled to the pixel member, the assisted-release mechanism applying a force to the pixel member in the second active state.
In another aspect, the present invention includes a method for switching a light signal in an optical switch. The optical switch includes a pixel movable between a light redirecting state and a non-redirecting state, and an actuator that applies a force to the pixel to thereby move the pixel from the redirecting state to the non-redirecting state. The method includes the steps of providing an assisted-release mechanism. The assisted release mechanism is pressed into the pixel member in the non-redirecting state to thereby store potential energy. The potential energy is released when the actuator ceases to apply the force to the pixel, whereby the assisted-release mechanism urges the pixel to move from the non-redirecting state to the redirecting state.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.